In processing wafers or substrates to integrated circuits (ICs) or semiconductor devices, an antireflective coating (ARC) is typically present beneath a photoresist layer to reduce the reflection of light used to pattern the photoresist layer, as part of patterning a nitride layer, such as silicon nitride (see, for example, U.S. Pat. No. 6,841,491). Thus, one common requirement in manufacturing ICs is the etching of openings in the ARC and the nitride layer to form features such as vias, contacts and/or trenches. Typically, these openings or features are formed through openings in a photoresist pattern by plasma etching using an energized etchant gas (plasma). Common etchant gases for plasma etching ARCs include mixtures of gases containing fluorine, such as C4F8/O2/N2, CHF3/CF4/O2/Ar, C2F6/Ar, or SF6 (see, for example, U.S. Pat. No. 6,699,795).
Although conventional etch chemistries or recipes are satisfactory for etching ARCs, they have generally not been suitable for etching nitride layers. Openings through the ARC and the nitride layer typically cannot be etched with the same recipe, in which openings are etched in the ARC. Thus, etching openings in the ARC and the nitride layer have been performed in two separate steps. In particular, conventional ARC etch chemistries have not been suitable or capable of etching a nitride layer overlying a second underlying oxide dielectric layer, such as silicon oxide (SiO2), with an acceptable selectivity to the underlying layer. Moreover, as the size of devices in ICs continues to shrink, the need for high selectivity is even more pronounced in order to etch nitride layers having areas of differing thicknesses, since the material underlying the thinner portions of the nitride will be exposed to the etch chemistry for longer periods of time.
Etch chemistries with fluorine containing gases are heavily polymerizing, and produce polymeric etch byproducts that deposit on the substrate and/or on surfaces in the chamber. These deposits can lead to defects in the substrates, which lower yields, and can lead to the need for more frequent cleaning of the chamber reducing substrate throughput. In addition, polymeric deposits on chamber walls are known to cause process shifts, drift and/or instability within the PM (preventive maintenance or cleaning) cycle of the chamber. Furthermore, alternating polymerizing and non-polymerizing processes often leads to flaking of the polymer deposited on the chamber, restrict or limit the running of these dissimilar etch chemistries in the same chamber.